JP2017538055A - Sound absorbing element and system - Google Patents

Abstract

A sound-absorbing element and a sound-absorbing system including a fibrous material having the following characteristics, that is, an inherent ventilation resistance of 527 to 1552 [Pa s / m] and a mass porosity of 66 to 79% are described. [Selection] Figure 2

Description

  The present invention relates to a sound absorbing element and a system.

  When sound waves emitted in a closed room strike a surface, some of the acoustic energy passes through the surface, some is absorbed by collisions with the surface, and some is reflected back into the room. Are known.

  If the amount of surfaces that are reflected in the room is large, the room can be very acoustically disturbed, i.e. sound waves generated in the room are amplified with an effect similar to echo.

  In order to improve the acoustics in a room without structural changes, it is known to use sound-absorbing material in the room, in particular adjacent to the surface (eg walls and / or ceiling) that partitions the room. Conventional sound-absorbing materials, as is known, have the property of absorbing at least a portion of acoustic energy and reducing the reflected energy portion.

  Patent document 1 (International Publication No. 2013/113800) by the present applicant describes a sound-absorbing panel including a padding layer having a first thickness, including a thermobonded synthetic fiber. At least a portion of the panel has a variable density that is dense in the outer layer region and low in the inner layer.

  Patent Document 2 (European Patent No. 2,472,018) describes a sound absorption system which is understood as a wall element having at least two supports with micropores and another support without micropores. Yes. A support without micropores is not surrounded by a support with micropores.

  The present applicant has noticed that the system described in Patent Document 2 is disadvantageously complicated and expensive to manufacture. In this system, in fact at least two supports are microporous and the micropores are regularly arranged on the surface of the support. Furthermore, the size of each micropore and the distance between one micropore and an adjacent micropore must be precisely controlled. The performance of the sound absorption system of Patent Document 2 actually depends strictly on such geometric parameters. The production of the system of US Pat. No. 6,057,096 is therefore rigorous and complex and relatively expensive to machine the support.

International Publication No. 2013/113800 Pamphlet European Patent No. 2,472,018

  The object of the present invention is therefore to obtain a sound-absorbing element that is less complex and less expensive to produce than the system according to US Pat.

  The inventor of the present application has tested the various materials and surprisingly realizes that a sound-absorbing element that is simpler and less expensive than the system according to Patent Document 2 can be manufactured using a fibrous material and in a single layer. discovered.

  More specifically, the inventor of the present application describes a sound absorbing element that is simpler and less costly than the system according to Patent Document 2, as described in detail below, with respect to the specific characteristics relating to the inherent ventilation resistance Rs and mass porosity. It has been discovered that it can be formed using natural or man-made fabrics having the following:

  The inventor advantageously has an inherent airflow resistance (sometimes simply indicated as Rs) lower than 414 [Pa · s / m] or higher than 2368 [Pa · s / m] and less than 60% or 81 A fibrous material having a mass porosity greater than% (sometimes referred to simply as PM) has low performance with respect to sound absorption and between 527 [Pa · s / m] and 552 [Pa · s / m]. Fibrous materials with inherent airflow resistance and mass porosity PM between 66% and 79% have good performance in terms of sound absorption and from 723 [Pa · s / m] to 1213 [Pa · s / m] A fibrous material having an inherent airflow resistance Rs between and a mass porosity PM between 74% and 77% has optimal performance with respect to sound absorption.

  Based on these properties, it is possible advantageously to identify a material suitable for the sound-absorbing element according to the invention. The present invention advantageously provides a sound-absorbing element and a sound-absorbing system that are simple and inexpensive to manufacture and that have optimal sound-absorbing characteristics.

According to the first aspect of the present invention, there is provided a sound-absorbing element comprising a fibrous material, having the following characteristics: an intrinsic ventilation resistance of 527 to 1552 [Pa · s / m], and 66% to 79%. A sound absorbing element having mass porosity is provided.

  Preferably, the fibrous material has an inherent ventilation resistance of 723 to 1213 [Pa · s / m] and a mass porosity of 74% to 77%.

  Preferably, the fibrous material comprises a woven fabric.

  More preferably, the fabric is an artificial fabric.

  Preferably, the warp of the fabric has a yarn count per centimeter in the range of 5 to 70.

  More preferably, the warp of the fabric has a yarn count per centimeter in the range of 5-40.

  Even more preferably, the warp of the fabric has a yarn count per centimeter in the range of 15-40.

  Preferably, the weft of the fabric has a yarn count per centimeter in the range of 5 to 70.

  More preferably, the weft of the fabric has a yarn count per centimeter in the range of 5-40.

  Even more preferably, the weft of the fabric has a yarn count per centimeter in the range of 12-22.

  According to some embodiments of the invention, the sound absorbing element comprises one or more layers of the fabric.

  According to a first aspect, the present invention provides a sound absorbing system comprising the above-described sound absorbing element and a surface operating in conjunction with the sound absorbing element.

  Preferably, the surface is located at a predetermined distance from at least a part of the sound absorbing element.

  Preferably, the distance is between about 1 cm and about 30 cm.

  The invention will become more apparent upon reading the following more detailed description presented as a non-limiting example with reference to the accompanying drawings.

1 shows a sound absorbing element having a single layer of fibrous material according to an embodiment of the invention operating in conjunction with a surface. It is the figure which looked at the sound absorption element and surface of FIG. 1 from the side. 6 illustrates another embodiment of a single layer sound absorbing element and system according to the present invention. 6 illustrates another embodiment of a single layer sound absorbing element and system according to the present invention. 6 illustrates another embodiment of a single layer sound absorbing element and system according to the present invention. Fig. 6 is a histogram showing the values of absorption parameters representing the absorption characteristics of a material set considered during the test. FIG. 6 is a graph showing diffuse incident absorption coefficient values measured for several materials considered by a certification authority. It is a histogram which shows the specific ventilation resistance value R of the tested material. It is a graph which shows the value of an absorption parameter as a function of intrinsic ventilation resistance. 2 is a histogram showing mass porosity values for tested materials. FIG. 6 is a graph showing mass porosity values as a function of intrinsic ventilation resistance and correlated to absorption parameter values. 1 shows a sound absorbing element having two fibrous material layers according to an embodiment of the invention operating in conjunction with a surface. 4 shows another embodiment of a two-layer sound absorbing element and sound absorbing system according to the present invention. 4 shows another embodiment of a two-layer sound absorbing element and sound absorbing system according to the present invention. 4 shows another embodiment of a two-layer sound absorbing element and sound absorbing system according to the present invention. 4 shows another embodiment of a two-layer sound absorbing element and sound absorbing system according to the present invention. 4 shows another embodiment of a two-layer sound absorbing element and sound absorbing system according to the present invention. It is a graph which shows the diffuse-incidence absorption coefficient value measured in the sound absorption element of a single layer and two layers regarding the material considered by a certification | certification authority. 3 shows another embodiment of a three-layer sound absorbing element and sound absorbing system according to the present invention. 3 shows another embodiment of a three-layer sound absorbing element and sound absorbing system according to the present invention. 3 shows another embodiment of a three-layer sound absorbing element and sound absorbing system according to the present invention. 3 shows another embodiment of a three-layer sound absorbing element and sound absorbing system according to the present invention. 3 shows another embodiment of a three-layer sound absorbing element and sound absorbing system according to the present invention. 6 shows yet another embodiment of a sound absorbing system according to the present invention. 6 shows yet another embodiment of a sound absorbing system according to the present invention.

  For the present invention and claims, unless expressly stated otherwise, all numbers expressing values, amounts, percentages, etc. are to be interpreted in each case as being preceded by the term “about”. I want you to understand. Further, all ranges are intended to include all combinations of the indicated range limits and all subintervals that may not be specifically described in the present invention.

  The present invention relates to a sound-absorbing element having a fibrous material designed to absorb at least part of the energy of sound waves generated in the environment in cooperation with a surface by a gap. The “sound absorbing system” according to the present invention includes a sound absorbing element and a surface on which the sound absorbing element operates in conjunction.

  The verb “cooperate” means that when a sound wave strikes the sound-absorbing element 1, the surface 2 receives part of the energy associated with the sound wave striking the sound-absorbing element 1 and reflects at least a part (towards the sound-absorbing element). To be understood as meaning.

  More specifically, when the sound wave reaches the sound absorbing element 1, a part of the energy is reflected and a part is transmitted. The transmitted energy is attenuated due to the material characteristics of the sound absorbing element 1 (particularly, when the sound absorbing element 1 is a woven fabric, the woven fabric transmits the transmitted sound wave due to the inherent ventilation resistance R and its porosity. Attenuate). Sound waves transmitted through the sound absorbing element 1 strike the surface 2 and are reflected by the surface 2. Therefore, the energy absorption of the sound wave impinging on the sound absorbing element 1 occurs as a result of attenuation of the sound wave energy caused by the material of the sound absorbing element 1 and as a result of the transmitted and reflected sound waves striking the gap between the element 1 and the surface 2. . In particular, absorption occurs at any frequency, but if the surface 2 is completely rigid and reflecting, the absorption will increase at several (equally spaced) frequencies based on the thickness of the air gap. In the case of normal incidence of sound waves on the surface 2, the first maximum absorption frequency is a frequency at which the thickness of the gap is ¼ of the wavelength length of sound waves with respect to that frequency.

  Referring to FIGS. 1, 2 and 3a-3c, a first embodiment of the present invention relates to a sound absorbing element 1 comprising a single layer of fibrous material.

  In particular, in the embodiment shown as an example in FIGS. 1 and 2, the sound absorbing element 1 is in the form of a flat panel. This embodiment is presented only as an example. The sound absorbing element 1 according to the present invention can take practically any form.

  The sound absorbing element 1 shown in FIGS. 1 and 2 operates in conjunction with the surface 2. According to the embodiment (shown in FIGS. 1 and 2), the surface 2 is a substantially flat surface. In other embodiments, the surface is not flat but can be wavy, reliefd, angled walls, and the like. Preferably, the sound absorbing element 1 is located at a distance D from the surface 2. The distance between element 1 and surface 2 can also be non-uniform. According to one embodiment, the element 1 can be attached to the surface 2.

  Therefore, the expression positioning the sound absorbing element 1 at a distance D from the surface 2 means positioning at least a part of the element at a distance D from the surface 2 (D being constant or variable).

  The surface 2 can be, for example, a wall or ceiling of a room in which the sound absorbing element 1 is positioned, a rigid panel or a permeable material. The distance D can vary from a minimum of a few centimeters (eg, 1-5 cm) to a maximum of 20 cm or more (which can be greater than 30 centimeters).

  FIGS. 3a and 3b show, by way of example, two adjacent views (an axonometric view on the left side) in two other possible embodiments of a single-layer sound absorbing element 1 where the distance between the element 1 and the surface 2 is not uniform. And a side view on the right side). In particular, in FIG. 3a, the element 1 is inclined with respect to the surface 2, and in FIG. 3b, the element 1 is helical. FIG. 3c is a side view of another embodiment of the sound absorbing element 1 in which the element 1 operates in conjunction with the horizontal surface 2 of the room, for example, the ceiling.

  Below, it is the test which this inventor conducted, Comprising: This test result regarding the characteristic of the fibrous material of the sound-absorbing element 1 by this invention recognized as a result is demonstrated.

  The inventor first selected a different set of fibrous materials for the test described above. This set has a material number equal to 31 and is denoted below by the reference signs M (1), M (2),... M (31), or M (i), i = 1,. These materials are made of Trevira CS®, a polyester, and have the following properties: thickness, porosity, weaving, number of wefts, number of warps, yarn processing, yarn Chemical fiber fabrics that differ from each other with respect to one or more of the numbers.

  Tables 1-3 show some properties for some materials considered. Table 1 shows the type of weaving, Table 2 shows the characteristics of the warp, and Table 3 shows the characteristics of the weft of the material considered.

  As can be seen from the table, each considered material is also shown as a single type of yarn (hereinafter also referred to as yarn 1, "yrn 1"), or two types of yarn (also known as yarn 1 and yarn 2, "yrn 2") ), Both with weft and yarn. A yarn consists of a set of filaments joined together to form a thread. In the columns “yarn 1” and “yarn 2” in Tables 2 and 3, the numbers in parentheses indicate the number of threads in each yarn.

  In Tables 2 and 3, the abbreviation “Dtex” is a unit of measurement of the linear density of the yarn and means “decitex”, which indicates the weight in grams of 10 km of the yarn.

  The term “texturized” indicates that the yarn has undergone a texturing process, which stabilizes the fiber shrinkage after the fiber has been spun and extruded as is known. A process that involves processing the yarn by a thermomechanical treatment.

  The term “taslanized” indicates that a taslan processing procedure, which is a processing process using a high-speed air jet, is known, as is known.

  The term “twisted” indicates that the yarn is formed by threads that are bonded and twisted together as a pair.

  “Cationic” yarns (typically polyesters) are yarns composed of threads of modified polyesters that can be dyed at boiling temperatures using cationic dyes or basic dyes, as is known.

  The present inventor further defined an absorption parameter indicating the sound absorption performance of the considered material. This parameter was defined as described below.

  Each of the materials considered was subjected to testing after being arranged in a vertical state (as shown in FIG. 1) approximately parallel to a flat surface separated by voids.

The considered material is in particular a subset of 20 materials, in this case a material M (i), a subset of iεI = {1-13, 21, 24-29}, about 20 m ³ Tested in a volumetric test room, measured by UNI Standard EN ISO 354: 2003 dated 1 December 2003 “Acoustics-Measurement of the sound absorption in a reverberation chamber” The test room volume and properties were maintained as follows. For each material, the diffuse incident absorption coefficient was measured taking into account three different voids (D = 50 mm, 100 mm, 200 mm). For each material and each void, the diffuse incident absorption coefficient was measured at six fixed points in the test room, and then the measurements thus obtained were averaged. The diffuse incident absorption coefficient was measured in a 1/3 octave band within the frequency range of 250 Hz to 6300 Hz.

  For each material and each air gap, within the frequency range considered, the inventor has obtained a diffuse incident absorption coefficient value of N = 15 (especially, as described above, each of these values has six measurements). Obtained from the average of the values). For example, the diffuse incident absorption coefficient values thus obtained for the material M (i), iεI = {1-13, 21, 24-29} are denoted by the notation C (i, j, k). Here, the index j = 1,..., N indicates the value of the diffuse incident absorption coefficient at a predetermined frequency, and the index k indicates the thickness value of the air gap considered for each measurement (for example, k = 1). Indicates D = 50 mm, k = 2 indicates D = 100 mm, and k = 3 indicates D = 2000 mm).

After this, for each material and for each thickness value of the air gap, k of the mean Cm (i, k), i∈I, diffuse incident absorption coefficient value C (i, j, k) in the considered frequency range = 1,2,3, i∈I, j = 1,..., N, k = 1,2,3 were calculated using the following equations.

  In this way, the average value Cm (i, k) of the diffuse incident absorption coefficient was related to each material M (i), i∈I with respect to the thickness of each gap.

Finally, for each material M (i), i∈I, to obtain a parameter indicating the “average” absorption characteristic of each material, the average value Cm of the diffuse incident absorption coefficient related to the three air gap thicknesses considered. (I, k) was further averaged. This parameter can be simply expressed below as “absorption parameter” and also using the notation CM (i). The corresponding absorption parameter CM (i) for each material M (i) is calculated using the following equation:

  FIG. 4 is a histogram showing absorption parameter CM (i) values for 20 materials M (i) and iεI considered by the inventors of the present application in order to evaluate the absorption parameters. As can be seen from FIG. 4, the materials M (3), M (6), M (10), M (24) and M (25) have the highest absorption parameter values (higher than 0.6). On the other hand, the materials M (4), M (7), and M (12) have the lowest absorption parameter values (lower than 0.5).

  In order to confirm the above results, a number of tests were carried out in the reverberation chamber according to the UNI standard EN ISO 354: 2003 described above by the test certification association “Istituto Giordano” in Gatteo (FC (Forli-Cesena), Italy). In particular, the present inventor conducted a number of tests in consideration of the materials M (4), M (11), M (12), M (20), and M (25).

  The results of these tests performed according to the UNI standard EN ISO 354: 2003 are shown in FIG. In particular, FIG. 5 shows fabrics M (4), M (11), as a function of frequency (along the x-axis), considering a gap of about 100 mm between the fabric and the flat surface (wall of the reverberation chamber). A graph of the diffuse incident absorption coefficient (along the y-axis) of M (12), M (20) and M (25) is shown. The frequency is expressed in Hz. The results are obtained in the test room and show the good reliability of the measured values described above, and the histogram shown in FIG. 4 is based on these measured values. Furthermore, the results show that the fabrics M (12) (absorption parameter CM (12) = 0.44) and M (4) (absorption parameter CM (4) = 0.41) are effectively M (25) (absorption parameter CM (25) = 0.63) and M (20), and the fabric M (11) (absorption parameter CM (11) = 0.56) indicates that the other fabric M ( 12), confirming that it is an intermediate result compared to M (4), M (20) and M (25).

  Based on the results obtained, in the following description and in the claims of the claims, the expression “poor performance” related to the sound absorbing properties of a material means that the material has an absorption parameter of less than 0.5. The expression “good performance”, understood to mean having and relating to the sound absorption properties of the material, means that the material has an absorption parameter between 0.5 and 0.6. As understood, the expression “optimum performance” related to the sound absorption properties of a material is understood to mean that the material has an absorption parameter of more than 0.6.

As is known (see “Acoustics. Materials for acoustic applications. Determination of the airflow resistance” in UNI standard EN 29053-1994), the inherent ventilation resistance Rs of a material quantifies the dissipation characteristics of acoustic energy in the material, It is also defined as:
Where ΔP [Pa] is the differential pressure between the two sides on both sides of the material compared to atmospheric pressure, and qv [m ³ / s] is the flow rate (velocity) of air through the material, A [m ² ] is a cross-sectional area of the material orthogonal to the air flow direction.

For each specific material M (i), i = 1,..., 31 tested, the inherent airflow resistance Rs (i) is determined by the following procedure:
a) A layer of material M (i) is bonded to a ring of plastic material (polycarbonate) with an outer diameter of 45 mm, and a Kundt's tube (so-called flat wave tube or impedance tube) with two microphones Positioning within the tube at a distance of about 100 mm from the end of the tube;
b) determining the apparent absorption coefficient of normal incidence in the frequency range of 100 Hz to 4200 Hz according to UNI Standard ISO 10534: 2001 "Acoustics-Determination of the sound absorption coefficient and the acoustic impedance in impedance tube-Transfer function method" Where this coefficient is denoted in the notation C ′ (i, j) as follows, where the M value of the normal incidence absorption coefficient in the frequency range considered (for example, the frequency interval at an interval of about 10 Hz): The index j = 1,..., M is taken to indicate the value of the absorption coefficient at a certain frequency,
c) determining the corresponding theoretical coefficient Cth ′ (i, j) for each apparent normal absorption coefficient C ′ (i, j) at normal incidence by obtaining: ,
Where ζs is expressed by the following equation:
Here, the notation Re {·} indicates the real part of the complex value, the notation | · | indicates the module of the complex value, Rs (i) is the intrinsic ventilation resistance of the material M (i), and Ms (i) [kg / m ² ] is the acoustic mass of the material, ω [rad / s] is the angular frequency, ρ ₀ [rad / s] is the air density, and c ₀ [m / s] is in the air And d [m] is the thickness of the gap between the material M (i) and the tube end;
d) determining the inherent ventilation resistance Rs (i) of the material M (i) for each given material M (i), which is the step of minimizing the following equation:
Here, as described above, C ′ (i, j) is a measured apparent absorption coefficient of normal incidence, Cth ′ (i, j) is a corresponding theoretical coefficient, and M is a considered frequency range. The number of absorption coefficient values for normal incidence at
e) dividing the resistivity value determined in this way by a correction factor equal to about 1.15, this correction factor being the normal incidence in the Kuntt tube carried out during step a) above Taking into account the presence of a ring of plastic material used during the measurement of the apparent sound absorption coefficient with respect to,
Estimated using the procedure consisting of:

  At the end of step e), the specific ventilation resistance Rs (i) of each considered material M (i) is determined.

  The measurement system includes a 45 mm diameter Kunt tube, two piezoelectronics model 378C10 nominal 1/4 "sound pressure microphones, a National Instruments (R) USB4431 board, and And a model NGS 1A power amplifier marketed by IG (San Marino).

  FIG. 6 is a graph showing specific ventilation resistance values Rs (i), i = 1,..., 31 for the considered material. As can be seen from the graph shown in FIG. 6, the inventor of the present application has found that the material-tested M (i) has an inherent ventilation resistance value Rs (i) in the range of 301 Pa · s / m to 2368 Pa · s / m. .

  Based on the absorption parameter value CM (i) shown in FIG. 4 and the specific ventilation resistance value Rs (i) shown in FIG. 6, the present inventor determines the tendency of the absorption parameter as a function of the specific ventilation resistance value for the material considered. did. FIG. 7 shows a graph of absorption parameter values (along the y-axis) as a function of the inherent ventilation resistance value (along the x-axis). The unit of measurement of the inherent ventilation resistance Rs (i) is Pa · s / m. As can be seen from the graph shown in FIG. 7, the inventor of the present application has found that a larger value of the absorption parameter can be obtained for the specific ventilation resistance value between 700 Pa · s / m and 1400 Pa · s / m.

As is known, the mass porosity PM of a material defines the percentage of air that is interconnected within a well-defined volume. The mass porosity PM is determined by the following equation:
Here, ρ is the apparent density of the material, and ρ _rif is the density of the reference material, that is, the material that forms the structure of the material. For example, if the reference material is the commercially available material Trevira®, its density ρ _rif is equal to about 1.38 g / cm ³ .

The inventor of the present application determines the ratio of the apparent density ρ (i) of each material M (i), i = 1,..., 31 to the surface mass of the material, that is, the mass of 1 m ² of the material and the corresponding thickness. Was calculated and determined. Both these parameters were measured during the test.

In order to measure the surface mass of each material M (i), the inventor considered a sample of the material M (i), recorded its area, and measured its weight using a precision balance. Appropriate transformations were made based on the data associated with the above reference material having a density of about 1.38 g / cm ³ , and the inventors obtained the surface mass of the material. The calculations and conversions described herein are based on theoretical data with a density equal to about 1.38 g / cm ³ of the material Trevira® and when using additives or different materials. Note that this value can be different. In this case, the calculation should be parameterized based on the new value.

Furthermore, in order to measure the thickness of the material M (i), the inventor adopts the procedure described in the UNI standard EN ISO 5084 and uses the thickness marketed by Solaco, Viera (Italy). A gauge D-2000-T was used under points 8.1, 8.2, 8.3 and 8.4. In particular, using a 20 cm ² press having a pressure of 1.0 kPa, and the temperature between 20 to 22 ° C., taking into account the permissible minimum water absorption of the polyester manufacturer declares (up to about 1.5%) The arithmetic average of the five measurements recorded at 45-50% air humidity was calculated.

Table 4 below shows the values measured for the surface mass, thickness and apparent density ρ (i) of the considered material M (i).

  FIG. 8 shows, instead, the mass porosity value PM (i), i = 1,..., 31 of the material M (i) calculated using the above equation [7].

  Based on the value of the specific ventilation resistance Rs (i) shown in FIG. 6 and the value of the mass porosity PM (i) shown in FIG. Determined the trend. FIG. 9 shows a graph of mass porosity PM (i) (along the y-axis) as a function of the inherent ventilation resistance Rs (i) (along the x-axis). The unit of measurement of the inherent ventilation resistance Rs (i) is Pa · s / m.

  Based on the value of the corresponding absorption parameter CM (i), the present inventor has determined the mass porosity PM (i) and specific ventilation resistance Rs (i) for the tested materials M (i), i = 1,. Values were grouped. In particular, in FIG. 9, which shows the mass porosity PM (i) as a function of the inherent ventilation resistance Rs (i), each value is related to the material M (i) and is indicated by a corresponding graph marker. The shape of the graph marker related to the material M (i) indicates the value of the absorption parameter CM (i) of the material M (i). The circular graph marker uses the value of the absorption parameter CM (i) (this value was obtained for the material in 20 subgroups of the 31 materials tested, as described above). Indicates a material that cannot.

The inventor of the present application is as follows:
A material with an absorption parameter lower than 0.5 as indicated by the square marker in FIG. 9, and thus a material with poor sound absorption properties, is less than 414 Pa · s / m or higher than 2368 Pa · s / m. And having a mass porosity of less than 60% or greater than 81%,
A material whose absorption parameter is in the range of 0.5 to 0.6 as indicated by the triangular marker in FIG. 9 and thus has good sound absorption characteristics, is between 327 Pa · s / m and 1552 Pa · s / m. Having an inherent ventilation resistance and a mass porosity between 66% and 79%,
The material has an absorption parameter higher than 0.6 as indicated by the star marker in FIG. 9, and thus a material with excellent sound absorption properties has an inherent ventilation resistance between 723 Pa · s / m and 1213 Pa · s / m, And having a mass porosity between 74% and 77%.

  Therefore, in conclusion, the present inventor has discovered that the performance of a material can be predicted with respect to sound absorption characteristics based on the material's mass porosity PM and inherent ventilation resistance Rs. For example, if the material has an inherent ventilation resistance of about 900 Pa · s / m and a mass porosity of about 75%, it can be expected that the material will have excellent performance with respect to sound absorption properties.

  According to another embodiment of the invention, the sound-absorbing element 1 can further comprise different layers of fibrous material arranged at some (constant or variable) distance from each other, this representation being on the surface 2 It is understood as meaning that the sound waves propagating towards the material sequentially hit several material layers.

  10 and 11a-11e show embodiments of the sound-absorbing element 1 having two layers of fibrous materials 11, 12 as some examples. Figures 13a to 13e show an embodiment of a sound absorbing element 1 with three layers of fibrous material as some examples. Figures 14a and 14b show other embodiments, which are described below. The sound absorbing elements shown in these drawings are presented as non-limiting examples of the present invention.

  According to different embodiments of the present invention, the layers of fibrous material are shown in FIGS. 10, 11a (left side isometric view, right side view) and FIG. 13 (left side isometric view, right side). The layers can be physically separated from each other and juxtaposed in parallel to each other, as shown in FIG. In particular, according to the embodiment shown in FIG. 10, the sound-absorbing element 1 can have two mutually separated parallel layers of fibrous material in the form of flat panels parallel to each other. 2) ". In particular, the sound-absorbing element 1 according to FIG. 10 has a first panel 11 positioned at a distance D1 from the surface 2 and a second panel 12 positioned at a distance D2 from the surface 2. In this case, the expression of positioning the first panel 11 (second panel 12) at a distance D1 (D2) from the surface 2 means that at least a part of the first panel 11 (second panel 12) is at a distance D1 (D2) from the surface 2. ).

  The inventor of the present application conducted a number of tests in order to measure the diffuse incident absorption coefficient of the sound absorbing element of the type shown in FIG. 10 by changing the fibrous material used for the panels 11 and 12. In particular, the present inventor conducted a number of tests at the test certification association “Istituto Giordano” in Gatteo (FC (Forli-Cesena), Italy) and diffused a sound absorbing element having two panels of material M (25). The absorption coefficient was measured. The results of these tests are shown in FIG. The frequency in Hz is shown along the x-axis. In FIG. 12, the square graph marker indicates the diffuse incident absorption coefficient of a single layer sound absorbing element (as shown in FIG. 1) formed of the material M (25) and having a 100 mm gap, and the triangular graph marker is the material M 1 shows the diffuse incident absorption coefficient of a single-layer sound-absorbing element (as shown in FIG. 1) formed of (25) and having an air gap of 200 mm, the elliptical graph marker is formed of material M (25), and the first panel 11 shows a diffuse incident absorption coefficient of a two-layer sound-absorbing element (as shown in FIG. 10) having a gap of 50 mm between 11 and surface 2 and a gap of 100 mm between the second panel and surface 2. The cross-shaped graph marker is made of material M (25), has a 100 mm gap between the first panel 11 and the second panel 12, and a 200 mm gap between the second panel and the surface 2. A two-layer sound absorbing element (as shown in FIG. ) Shows the diffuse incident absorption coefficient.

  As can be seen from the graph of FIG. 12, the presence of the double panel of the fibrous material M (25) allows the sound absorbing element 1 to be improved in terms of sound absorption compared to the case where the sound absorbing element 1 has a single panel of the material M (25). Performance is improved. Improved performance can be noticed particularly at frequencies higher than about 600 Hz. This performance is further achieved with a gap between the first panel 11 and the surface 2 formed of the material M (25) and between the second panel 12 and the first panel 11 even for frequencies lower than 600 Hz. This is improved when the thickness of the voids increases.

  FIGS. 11 b to 11 d show several embodiments of the sound-absorbing element 1 in the form having two layers of fibrous material. Each of these drawings shows an axonometric view of the sound absorbing element 1 on the left side and a side view of the sound absorbing element 1 and the surface 2 on the right side. As shown in the drawings, the distance between one layer and an adjacent layer is not uniform (eg, one layer can be inclined with respect to the adjacent layer as shown in FIG. 11b). Furthermore, as an alternative, the layers can be attached to each other, as shown in FIGS. 11b and 11c, or the fibrous material can be obtained from sequential fold lines as shown in FIG. 11d. FIG. 11e is a side view of another embodiment of the two-layer sound-absorbing element 1, in which case the element 1 operates in conjunction with a horizontal surface (eg a ceiling) of the room.

  FIGS. 13b to 13e show several embodiments of the sound-absorbing element 1 in the form of three layers of fibrous material. These embodiments correspond to the embodiments shown in FIGS. 11b-11e described above and will not be described further.

  Figures 14a and 14b show side views in two other embodiments according to the invention, in which one or more fibrous material layers of the sound-absorbing element 1 are positioned on both sides of the surface 2 which is a rigid panel . The panel 2 can be a fixed panel or a movable panel by a wheel or equivalent means. The fibrous panel can be physically separated from the rigid panel as shown in FIG. 14a and positioned in parallel, or attached to the panel 2 on one or both sides of the panel as shown in FIG. 14b. .

1 Sound absorbing element 2 Surface

Claims (10)

A sound-absorbing element (1) comprising a fibrous material, having the following characteristics:-Natural ventilation resistance of 527 to 1552 [Pa.s / m] and-Mass porosity of 66% to 79% element.   The sound-absorbing element (1) according to claim 1, wherein the fibrous material has an inherent ventilation resistance of 723 to 1213 [Pa · s / m] and a mass porosity of 74% to 77%.   The sound-absorbing element (1) according to claim 1 or 2, wherein the fibrous material comprises a woven fabric.   The sound-absorbing element (1) according to claim 3, wherein the fabric is an artificial fabric.   The sound-absorbing element (1) according to claim 4, wherein the warp of the woven fabric has a yarn number per centimeter in the range of 5-40.   The sound-absorbing element (1) according to claim 4 or 5, wherein the weft of the woven fabric has a yarn number per centimeter in the range of 5-40.   The sound-absorbing element (1) according to any one of claims 3 to 6, comprising one or more layers of the fabric.   A sound absorbing system comprising the sound absorbing element (1) according to any one of claims 1 to 7, and further comprising a surface (2) operating in conjunction with the sound absorbing element (1).   The sound absorption system according to claim 8, further comprising the surface (2) at a position away from at least a part of the sound absorption element (1) by a predetermined distance (D; D1, D2). 10. The sound absorbing system of claim 9, wherein the distance (D; D1, D2) is a distance between about 1 cm and about 30 cm.